Give horse archers shitty riding skill so that they can at best mount saddles/desert horses, therefore making light cav useful by using their speed to chase down horse archers or something along those lines.

What would be possible and what would be likely to change, even if there were a group willing to do this?
I mean I like the sound of the idea but it might turn the mod into one of the shitty copies of PW with too many gimmicks.